The only major school-wide traditional events I remember from the DU of the 80s were Homecoming and Winter Carnival. Those were the two big events that almost everyone attended.

DUPB would put on some one-off lectures, concerts and movies, but most of the smaller traditions were more specific to dorms and fraternities, such as Towers Jam and of course there were Greek traditions specific to particular fraternities, such as Kappa Sigma's Beachcombers Ball, Sigma Chi's Derby Days, DG's Anchor Splash, ATO Bar Nights, etc.